What's causing our hamster's patches?

My daughter's two-year-old male Syrian hamster has developed a black patch on his side, and a smaller one on the other side.

- DR DAVID GRANT

Do hamsters suffer from skin tumours, for example malignant melanoma? I'm concerned that this is the case here.

The black patches are unlikely to be tumours. It is quite common to be asked about these patches and many owners, like you, worry that they could be cancerous. They are often mistaken for melanomas.

Black patches are much more likely to be scent glands, which are often very prominent in male Syrian hamsters, and used to mark territory. The key things that distinguish them from tumours is that they exist on both flanks at the same site, and don't extend.

Having said that it is possible for a scent gland to become cancerous, although only rarely.

As with most animals, hamsters do suffer from a variety of tumours, including skin, which tend to occur in old age.